Electric switch



Dec. 2.4, 1957 w.'H. scHMELlNG 2,817,727

ELECTRIC SWITCH Filed Nov. 26, 1954 f w/f #s 5 "gia W f I.. l s!!! l IN VEN TOR.

United States Patent O ELECTRIC SWITCH William H. Schmeling, Dayton, Ohio, assignor to Generai Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 26, 1954, Serial No. 471,321

7 Claims. (C1. 20o- 83) This invention relates to electric switches and more particularly with a switch that is to be used in connection with a fluid pressure system.

The switch according to the present invention is characterized by its -simplicity of construction, economy in cost of manufacture, and reliability of operation in an efcient manner.

It is an object of the present invention to provide an improved switch structure that is adapted to be used in connection with uid pressure systems such as a hydraulic brake system of an automobile for controlling the operation of a signal device such as a stop light.

It is well known that various forms of pressure operated switches such as stop light switches have been here tofore proposed but all of these possess certain technical or practical disadvantages. These disadvantages have materially limited the commercial use of hydraulic switches as they have been found to be susceptible to leakage. This type of failure is particularly objectionable when the switch is installed in a hydraulic brake pressure system of a vehicle as fatal vehicle accidents may occur when leakage in the stop-light switch causes a failure of the brake system.

It is an object of the present invention to minimize the possibilities of leakage in a pressure operated switch by including an actuator of extremely rugged construction which has its sealing eifect increased as the actuating pressure is increased.

It is another object of the present invention to provide a uid operated switch with a member that serves both as a diaphragm and a contact actuator so as to provide a switch that will operate efliciently with the minimum number of moving parts.

It is a further object of the present invention to provide an actuator in a fluid pressure actuated switch that is formed of a unitary body of elastomeric material to have predetermined shape to tit in an opening of corre* sponding shape, said actuator having a pressure actuated surface and a contact moving surface so that the body material of the actuator may be crowded through a converging opening into a cylindrical passage to effect a greater distance of travel of the contact moving surface relative to the distance of travel of the pressure actuated surface.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Figure l is a cross-sectional View of a switch accord ing to the present invention.

Figure 2 in cross-section shows a modified form of the switch in Figure 1 with a bridging member in an open circuit position.

Figure 3 is a cross-sectional view of the switch in Figure 2 with the switch parts in a closed circuit position.

ICC

Figure 4 is a cross-sectional view of another modification of the switch shown in Figure l.

In the drawings, the numeral 20 designates a pressure actuated switch that is particularly adapted to be connected with and be actuated by the iluid pressure of a vehicle hydraulic brake system, not shown. it has been found that the pressures within a typical hydraulic brake system may rise to a pressure in the order of 1500 to 2000 p. s. i. when full pressure is applied to the brake cylinders. This high pressure may cause a brake system to fail in the event of leakage in any of the component parts such as the pressure operated switch which closes a circuit to the indicating light. The switch according to the present invention is particularly adapted to operate under the wide range of pres-sures that is experienced in the hydraulic brake system and to perform its operation without leakage. This is accomplished by the coniiguration of the shaped passage 22 in the housing 24 of the switch 20 and the coniiguration of the actuator means 26, all of which will be hereinafter more fully described.

The passage 22 in housing 24 extends from a flared opening 28 on o-ne end 29 to a chamber 3i) as located in the other end 31 of the housing 24. The walls 32 of the passage 22 are formed to converge in a radius to form the venturi or flared opening 28 which leads into a cylindrical bore 34 which extends to chamber 30. A closure 36 is suitably secured to the other end 31 of the housing 24 to close chamber 30. The securement of closure 36 to housing 24 is accomplished when the extending metal rim or tangs 38 are peened over the exterior surface rim on the closure 36. This closure 36 is preferably formed of a suitable insulating material and serves to position stationary contacts i0 and 42 within the chamber 30. The stationary contacts 40 and 42 are preferably sealingly embedded in the material of closure member 36 and extend therethrough to provide terminal ends 44 and 46, respectively, which may be connected in an indicating lamp circuit.

The end 29 of housing 24 is provided with a cap 48. This cap 43 is sealingly secured to housing 24 when a peripheral rim 50 of actuator 2o is compressed between a flanged portion S2 of cap 43 and an annular surface 27 on the housing end 29 which surrounds opening 2S. The securing of the cap 4S to the housing may be accomplished in any suitable manner as by beading the extending portions 54 on ilange 52 over a rim on the exterior of housing 24. The cap 48 has a threaded opening 56 on one end that is connectable with a source of variable uid pressure, not shown, such as the hydraulic brake system of a vehicle. This cap 4S serves to close the venturi dared opening 28 and defines a pressure chamber 58 that is in communication with the huid pressure source.

A bridging member 60 is also provided in chamber 30 in each of the switches 20 as shown in the drawings so as to form an electrical connection between the contacts 40 and 42. This bridging member 6d is normally held out of engagement with contacts and 42 and in the embodiments shown in Figures l and 2 normally rests on a wall 62 of chamber 30. in Figure l the bridging member 60 is maintained in engagement with the wall 62 by a spring 64 that is positioned by a recess 65 in closure member 36 and disposed between the bridging member 60 and the closure member 36.

The actuating means 26 for moving bridging member 60 into engagement with contacts 40 and 42 is preferably molded of a suitable elastomeric material such as natural, or synthetic, rubbers or mixtures thereof as are all well known to those skilled in the art. The actuator 26 is a unitary elastomeric part and is shaped to be snugly re ceived and conform to the configuration of the venturi or ared passage opening 28 and extend at least partially asie/,aar

3 'into the cylindrical bore 34 which 'leadsto chamber 30. rThe heretofore mentioned rim 50 is also integrally formed with the other body portions of actuator 26.

`When actuator .26 is installed inthe shaped passage 22 it preferably has one end 66 in contact with bridging member 60 as it rests on wall A62 `and has the other end 68,which maybe concave in shape, ina position to form one of the walls of pressure chamber S8. The elastomeric material selected for actuator 26 must be of the type which will readily deform without a compressive volume change. Thus when the pressure in chamber 58 increases, end 68 of actuator 26 is forced toward the venturi opening rThis causes the material of the body of actuator 26 to be simultaneously forced against the converging curved walls 32 so as to increase the pressure seal therebetween and to be crowded or forced so that the material in a sense flows from the opening 32 into the cylindrical bore 3d. 'l'he material in bore 32 is forced thereby toward chamber 30 and moves the bridging member 60 into engagement with the stationary contacts 4G and d?, so as to complete a circuit therebetween. From the above it is apparent that because the material of actuator -26 is deformable but not compressible, a small moveh ment of end 68, because of the large surface area which is in contact with the fluid pressure, will cause a large volume of the body material of the actuator to be moved so that the end 66 will be moved a substantial distance relative to the small movements of end 68. Further, when the pressure in chamber is reduced, the actuator, because of the resilient characteristics of the material from which it is formed, will tend to return to its normal shape and will cause the engagement between contacts 40 and 42 and bridging member 60 to be broken. This characteristic of the actuator 26 is utilized in the embodiment shown in Figures 2 and 3 wherein the bridging member is suitably connected to the actuator 26 as by means of a rivet 9d that has one end peened over the bridging member 6ft and the other end embedded, and joined as by cernenting or bonding, in the material of actuator 26. Thus the bridging member 6l) will reciprocate in response to the movement of end 66 of the actuator without the aid of a spring means such as spring 64.

In the embodiment in Figure 4, the bridging member 60 has its periphery secured in the walls of chamber 3ft and is provided with a snap action. This may be accomplished in any well known manner as by stretching the center portion of member 6@ so that it will oil can and snap over its center when it is moved by the rivet 92 which has one end suitably secured in the material forming the end 66 of actuator 26 and has the other end formed to have a lost motion connection with the snap acting bridging member dil. Thus in Figure 4 when the bridging member 6l) is to be moved to the right in response to a pressure increase in the switch 20, the end 66 will move the member 6ft until it passes over center when it will snap to the position shown in dotted lines to engage contacts 40 and 42. When the pressure in chamber 58 is decreased so that the end 66 is moved to the left, the head of rivet 92 will move the bridging member 6ft until it passes over its center so that the remaining distance of travel may occur with a snap action as is permitted by the lost motion connection as provided by the extending shank of rivet 92.

From the above it is apparent that the shape of passage 22 and actuator 26 may be modified without departing from the spirit of the present invention. Thus the shape may be conical or that of' a pyramid and the actuator may be formed without extending into the cylindrical bore, provided that the shape of the actuator is such that the elastomeric material will be forced along an inclined surface towards a restricted opening so that the movement of the ond toward which the material is forced is relatively greater than the end whereon the deforming pressure is exerted and further that because of the relative shape of the actuator 'and lthe w'alls against which the actuator is forced, the sealing between the actuator and walls is increased as the deforming pressure is increased.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

l. A pressure actuated switch, comprising in combination; a housing having a shaped passage therethrough, said passage having curvilinearly shaped walls converging from an opening on one end of said housing to a cylindrical bore leading to a chamber disposed in the other end of said housing, a closure for said chamber carrying stationary contacts within said chamber, a bridging member within said chamber normally held out of engagement with said contacts, a cap for the first mentioned end of said housing defining a hydraulic fluid pressure chamber, and an actuator for moving said Vbridging member in response to pressure variations in said chamber, said actuator comprising a unitary solid member formed of elastomeric material and normally shaped to conform to the shape of and completely fill said passage and extend partially into said bore, said member having one end operatively connected with said bridging member a flange on the other end of said member secured between said housing and cap for maintaining said member in said passage, said concave surface on the other end being constructed and arranged for forming a wall of said pressure chamber and adapted to be deformed in shape in response to variations in pressure in said chamber so that the movement of the end connected with Said bridging member is increased relative to said other end as the material of said actuator is compressed by the converging walls of said housing.

2. A pressure actuated switch comprising; in combination, a housing having a curvilinearly shaped chamber on one end and a flared opening on the other end, a closure for said chamber, cooperating contacts in said chamber one of which is normally out of engagement with the other, a cylinderical passage extending through said housing from the chamber end and forming an extension of said flared opening, a cap for said other end for defining a hydraulic fluid pressure chamber with said opening, and a means for moving said one contact into engagement with the other contact in response to an increase in pressure in said chamber, said means including; a unitary member of elastomeric material shaped to conform to and completely fll said flared opening and extend partially into said cylindrical passage, a peripheral flange integrally formed on said member interposed between said housing and cap for forming a seal therebetween and for maintaining said member in position in said opening and a concave surface in said chamber arranged to be deformed by pressure variations in the chamber.

3. A pressure actuated electric switch, comprising; in combination, a housing having a chamber on one end and an opening having curvilinearly shaped flared walls in the other end, a closure for said chamber, cooperating contacts in said chamber one of which is normally maintained out of contact with the other, a cylindrical passage in said housing having walls forming a continuation of the walls of said flared opening and extending through said housing to said chamber, a cup for the other end of said chamber defining a hydraulic fluid pressure chamber with said opening, and a means for moving said contacts into contacting engagement in response to an increase in pressure in said chamber, said means including; a unitary member of solid elastomeric material having a cylindrical portion a flared end portion a concave surface on the flared end portion, said means normally being positioned within said housing in contact with the walls of said cylindrical passage and said flared opening a flange integrally formed on the periphery of the flared end of said member adapted to form a seal between the cap and housing and constantly maintain said member in said passage as said member is deformed by pressure variations in said chamber.

4. A pressure actuated switch, comprising; in combination, a housing having a chamber on one end and an opening having curvilinearly shaped flared walls in the other end of said housing, a closure for said chamber, cooperating contacts in said chamber, one of which is normally maintained out of contact with the other, a cylindrical passage in said housing having walls forming a continuation of the walls of said ilared opening and extending through said housing to said chamber, a cup for the other end of said chamber defining a hydraulic uid pressure chamber with said opening, and a means for moving said contacts into contacting engagement in response to an increase in pressure in said chamber, said means including; a unitary member of solid elastomeric material having a cylindrical portion and a ared end normally positioned within said housing in contact with the walls of said passage and said opening, an integral ange on the periphery of said flared end that is secured between the cup and housing for constantly maintaining said member in position in said passage, a concave surface surrounded by the flange, and in contact with the fluid in the chamber said unitary member being responsive to pressure variations in said chamber and adapted to have the material thereof radially compressed by the flared walls of said opening whereby the material in said cylindrical passage is longitudinally extended for causing increased movement of the material in said passage relative to the material in said opening.

5. The switch as set forth in claim 1 wherein the bridging member is normally maintained out of engagement with the contacts and in operative contact with the actuating member by a spring that is positioned between said bridging member and the closure member.

6. The switch as set forth in claim 1 wherein the bridging member has a portion thereof embedded in the material of said actuator.

7. The switch as set forth in claim 1 wherein the bridging member is snap acting and is connected with said actuator through a lost motion connection.

References Cited in the tile of this patent UNITED STATES PATENTS 1,909,699 Mahan May 16, 1933 2,260,636 Neff Oct. 28, 1941 2,275,556 Rasmussen Mar. 10, 1942 2,368,181 Vernet Jan. 30, 1945 2,430,428 Katcher Nov. 4, 1947 2,439,561 Cressey Apr. 13, 1948 2,466,111 Katcher et al Apr. 5, 1949 2,548,878 Dillman Apr. 17, 1951 2,587,482 Keller Feb. 26, 1952 

